HrMs O 13 (Lt.Cdr. Eduard Herbert Vorster, RNN) left Dundee to patrol near the entrance of the Skagerrak on 12 June 1940. She failed to return to Dundee on 21 June 1940 and was declared overdue on the 24th.

So far the wreck has not been located. A search was sheduled to take place in October 2012 but had to be cancelled due to bad weather in the search area.

29 May 1940HrMs O 13 (Lt.Cdr. E.H. Vorster, RNN) departed Portsmouth for her 1st war patrol. She was ordered to pstrol in the English Channel. (2)

1 Jun 1940At 0100 hours HrMs O 13 (Lt.Cdr. E.H. Vorster, RNN) sighted 'what was thought to be' an enemy submarine in position 49°54'N, 00°46'W. This submarine was seen to fire two White Very lights. O 13 dived but did not attack. [No German submarine was operating in this area, if it was a submarine it was more likely an Allied one as several were operating in the English Channel, so far we have been unable to match one.]

Later the same day HrMs O 13 ended her 1st war patrol at Portsmouth. (2)